Miniature electrical switch



Feb. 24, 1970 'A. BLATTER MINIATURE ELECTRICAL SWITCH Filed Aug. 21, 1968 1 I J a INVENTOR. well 5&3?!

United States Patent 3,497,651 MINIATURE ELECTRICAL SWITCH Albert Blatter, Southfield, Mich., assignor to The Bendix Corporation, a corporation of Delaware Filed Aug. 21, 1968, Ser. No. 754,309 Int. Cl. H01h 35/40 US. Cl. 200-83 5 Claims ABSTRACT OF THE DISCLOSURE SUMMARY OF THE INVENTION As the state of the art of fluidics advances, the need i for interface elements for control and readout functions increases. Many of the present output devices adapted for a pneumatic or hydraulic interface utilize a mechanical motion to provide either power or information to visual indicators or electrical switches. In order to be compatible with fluidics and fluidic circuitry as it presently exists and as forseen for the future, the electrical switch interface devices must combine small size with high sensitivity to small pressure changes and have low compression volumes. It is, therefore, an object of this invention to provide an electrical switch combining small size and low compression' volume with high sensitivity to small pressure changes. It is also an object of the present invention to combine these characteristics in a, switch which is reliable, low in cost, and easily assembled.

Since diaphragm type switches are well-known and provide dependable service, it is a further object of the present invention to provide an electrical switch which has a diaphragm-like action, but which utilizes a totally different means of contact enclosure. Since fluidics circuitry makes use of small diameter channels and passages through which relatively low volumes of fluid are passing, it is a still further object of the present invention to provide an electrical switch structure which achieves a diaphragmlike action through a small volume of compressive displacement so that the eflct of the presence of the switch on the fluid signal is minimal.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 shows, in section, an electrical switch made in accordance with the teachings of the present invention. For clarity, the contacts are shown closed without showing compression to the elastomeric member.

FIGURE 2 shows, in section view taken along line 22 in FIGURE 1, the fluid operated portion of the electrical switch made according to my invention.

DETAILED DESCRIPTION OF THE DRAWING Referring now to FIGURE 1, the switch made according to my invention has an enclosure body designated generally by 10. The enclosure includes a mounting member 12 and outer housing member 24. The mounting member is adapted for mating with an appropriate connector (not shown) of a fluidic system or the like having at least two pressure levels. In this preferred embodiment, this connection is of the push-in variety, but the man skilled in the art will recognize that the mounting member ICE 12 and the form of the connection may be altered within the scope of the invention to suit a particular application. The mounting member 12 has a bore or passage 14 into which is inserted the closed end 16 of the elastomeric member or boot 18. The boot 18 has a generally-annular collar or flange 20 at its open end.

An electrical body means comprised of inner housing member 22, epoxy potting 34, switch contact members 26 and 28 and electrical leads 30 and 32 is retained within the outer housing member 24 by crimping of the ends of member 24 so as to compress the collar 20 of elastomeric boot 18 between the mounting member 12 and the electrical body means. The interior of the elastomeric member 18 extending into the interior of bore 14 defines a chamber 25 which is fluid tight due to the compression of the collar 20 between mounting member 12 and the electrical body means. The switch contact members 26 and 28 extend into the chamber 25. The switch contact members 26 and 28 are mutually crimped to the electrical leads 30 and 32 of an electrical output means (not shown) such as a relay or an indicator or the like. The switch contact members 26 and 28 and the electrical leads 30 and 32 are mechanically held in place within the inner housing member 22 by the epoxy potting 34 which also serves to electrically insulate the switch contact members 26 and 28, the electrical leads 30 and 32 and the inner housing 22 from each other. Vent 36 is provided to communicate ambient air pressure through the electrical body means to the chamber 25.

Projection 38 on the remote free-end of switch contact member 28 is operative to make contact with switch contach member 26 and permits electrical contact upon minimum movement of the remote free-ends of the switch contact members 26 and 28 while allowing the members 26 and 28 to be spaced substantially farther apart along the major portion of their length. This reduces capacitive coupling between the switch contact members 26 and 28 while providing the switch with improved sensitivity to pressure changes and a relative insensitivity to nonuniformities in the boot 18.

FIGURE 2 shows a section view of my switch with the section taken through the projection 38. Boot 18 is shown as having a first lateral dimension which is significantly greater than the second lateral dimension taken perpendicular to the first lateral dimension. The switch contact members 26 and 28 lie substantially parallel to this first lateral dimension and compression or collapse of the boot 18 will succeed in bringing the projection 38 and the freeend of switch contact member 26 into electrical current conducting contact. By providing the boot 18 with greatly differing lateral dimensions, a preferred direction of collapse is established so that when the fluid pressure on the exterior surface of the boot 18 exceeds the pressure on the interior surface of the boot 18, it will collapse bringing together the contactive ends of the switch contact members 26 and 28.

From a consideration of FIGURES 1 and 2 together it will be seen that boot 18 is a generally tubular member closed at the insertion end 16. The boot 18 is preferably made of a one-piece elastomeric material selected to be inert and unreactive in the presence of the fluid for which the switch is contemplated. The material selected must also be flexible with the temperature range of switch operation. By providing boot 18 with dissimilar lateral dimensions, a preferred direction of collapse will be established. By providing a relative long and broad surface on both sides of the boot 18, a diaphragm-like switch action is provided to initiate cantilever closure of the contact members in a switch inherently capable of use in locations smaller than those in which a diaphragm switch may effectively be used. The vent 36 serves to permit collapse of the boot 18 without compression of the fluid inside the boot 18 in those systems having operating pressure levels above and below ambient air pressure. Vent 36 will also allow modification of the fluid pressure withinthechamber 25 for those systems which operate entirely above or entirely below ambient air pressure.

The contact switch members 26 and 28 are shown separate from the sleeve 16, but they could also be incorporated within the sleeve material in the sleeve molding operation. Upon reduction of the fluid pressure outside of the sleeve, the natural resiliency of the sleeve material will cause it to assume its relaxed position with the inherent resiliency of the contact switch members 26 and 28 being sufficient to separate their contactive free-ends. To prevent arcing and contact welding, an arc suppression means should be incorporated in the circuit with which the switch is associated unless current levels are kept quite low.

I claim:

1. A pressure sensitive electrical switch comprising:

an enclosure means;

an electrical body means retained within said enclosure means and including a pair of extending contact members;

said contact members adapted to establish current conducting contact at a location remote from said electrical body means;

an elastomeric boot clamped in fluidtight fashion between said enclosure means and said electrical body means;

. said boot defining a fluidtight chamber around said contact members; and 7 said contact members and said boot extending away from the electrical body means a substantial distance to allow closure of said contact members by cantilever movement.

2. A pressure sensitive electrical switch comprising:

a mounting member adapted for attachment to a fluid system having at least two pressure levels and having a bore in communication with said system;

an electrical body means;

an outer housing member interconnecting said mounting member and said electrical body means;

a generally tubular elastomeric member clamped in fluidtight fashion between said electrical body means and said mounting member and extending into the bore thereof;

said elastomeric member defining a fluidtight chamber within said bore and having a noncircular cross section wherein a first lateral dimension is significantly larger than a second lateral dimension which lies perpendicular to said first lateral dimension thereby establishing a preferred direction of collapse in response to increase in the fluid pressure external to said elastomeric member; a pair of switch contact members extending from the electrical body means into said chamber; and said pair of switch contact members having a pair of contact ends lying in a spaced-apart relationship in the direction ofsaid second lateral dimension. 3. The switch as claimed in claim 1 wherein: said boot has a first lateral dimension significantly greater than a second lateral dimension which lies perpendicular to said first lateral dimension thereby establishing a preferred direction of compression of said boot. 4. The swtich as claimed in either of claims 1, 2, and 3 including:

vent means contained within said electrical body mean operative to communicate the interior of said chamber to a region external to the electrical body means. 5. The switch as claimed in claim 4 wherein one of said contact members includes a projecting portion remote from said electrical body means and extending toward the other of said switch members to provide reduced travel distance for switch closure.

I References Cited UNITED STATES PATENTS 2,238,327 4/1941 Jackson et a1. 200-819 2,419,942 5/ 1947 Brewer.

3,254,199 5/ 1966 Weinstein 2-008l.9 XR 3,369,089 2/ 1968 Hellman ZOO-81.9 3,421,124 1/1969 Kidd.

FOREIGN PATENTS 405,704 2/1934 Great Britain. 1,121,165 1/1962 Germany.

ROBERT S. MACON, Primary Examiner I. R. SCOTT, Assistant Examiner U.S. c'1. X.R. zoo-81.9 

